When a user performs Google searches, there is an expectation of privacy regarding at least two types of information:

Personally identifiable information

Searches

Google's privacy policy for using aggregated search data is described here:

"We may share with third parties certain pieces of aggregated, non-personal information, such as the number of users who searched for a particular term, for example, or how many users clicked on a particular advertisement. Such information does not identify you individually."